Demand for NAND-type flash memories is rapidly increasing along with an increase in different uses of the NAND-type flash memories for processing large amounts of data, such as images and dynamic images, in mobile appliances. Recently, readout/write of data in NAND-type flash memories at a single power supply voltage or a low-voltage supply voltage has been necessary, and a step-up circuit for supplying a step-up voltage or a negative step-up voltage has been provided for each operation. However, these circuits require a significant area of the memory device.